采用X-射线衍射及恒电位阶跃计时电流法测定了不同炭材料的结构及锂在这些炭材料中的扩散系数.发现炭电极的放电程度与结构对锂在炭电极中的扩散系数有重要影响.随着放电程度的增加,锂在MCMB电极中的扩散系数由4.43×10-9 cm2/s减少到5.24×10-10 cm2/s,在50%的放电程度下,锂在蔗糖热解炭、树脂热解炭、人造石墨及MCMB中的扩散系数分别为1.4×10-10 cm2/s,5.75×10-10 cm2/s,1.24×10-9 cm2/s,2.1×10-9 cm2/s.与无定形碳如蔗糖热解炭及树脂热解炭比较,锂在石墨化炭如人造石墨、MCMB中的扩散要容易得多.
The structures of pyrolytic sugar carbon, resin carbon, artificial graphite, and mesocarbon microbeads (MCMBs) and the diffusion coefficient of lithium in them were determined by X-ray diffraction and potential step chronoamperometry measurements. It was found that the diffusion coefficient of lithium was strongly dependent on the degree of discharge and the structure of the carbon anodes. As the discharge degree increased, the diffusion coefficient of lithium in MCMB anodes decreased from 4.43 × 10 -9 cm2/s to 5.24 × 10 -10 cm2/s. At half discharge, the diffusion coefficients of lithium in sugar carbon, resin carbon, artificial graphite, and MCMB anode were 1.4 × 10-10 cm2/s, 5.75 ×10-10 cm2/s, 1.24 × 10-9 cm2/s, 2. 1 × 10-9 cm2/s, respectively, showing that diffusion of lithium in soft carbons (artificial graphite and MCMBs) was much easier than in hard carbons such as sugar and resin carbon.
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